Screenshot from ULA Webcast of the launch of NROL-44
Mission Rundown: ULA - Delta IV Heavy - NROL-44
Written: September 5, 2021 - Edit: November 29, 2022
And the gist of this is...
In a succession of launches for the National Reconnaissance Office (NRO), United Launch Alliance returns with NROL 44. This launch is for the NRO, noting much is known about the size, mass, and capabilities of the payload.
This was the 12th launch of a Delta IV Heavy at 20:09 EST on December 10, 2020.
NOTAM with three splashdown areas. A is launch failure. B is Delta side boosters. C is the Delta core booster and fairing parts. There is no DCSS splashdown area specified
After 7 attempts NROL-44 finally launched. The Delta IV Heavy was prepared for launch in the summer of 2019 by being onsite and made ready for launch June 28, 2020, but the launch was delayed to August 26 for unknown reasons then moved to August 27 by request of the customer NRO.
The aging pad 37B ground equipment wasn’t properly maintained, so first a pneumatic sensor failed to perform properly. Two days later another pad abort was caused by a faulty helium valve with a broken rubber seal that failed to open the port Delta booster oxygen valve just prior to launch at T-00:00:03 seconds. Apparently outside helium pressure spins up the Delta IV Heavy turbopumps during startup. This must save weight.
September 26 the Delta IV Heavy was made ready for launch once again and postponed 24 hours because of a swingarm retraction issue then to 48 hours, because the launch tower's components are mostly 20 years old.
On September 28 the launch was scrubbed due to thunderstorms, and the next day a major hydraulic leak was discovered in the launch tower's swingarm retraction systems, which led to a major refurbishment of these systems of valves, hoses and replacement of at least 2000 gallon new hydraulic fluids.
October 1 they tried to launch for a sixth time but a valve in the Delta IV Heavy’s RS68A engines didn’t cooperate, so it was scrubbed again. It read closed when it actually was open. Delta IV Heavy consists of a million parts, and some can fail in two ways.
The NROL-44 Payload
Because United Launch Alliance has built up the reputation over the past few decades of being an incredibly reliable launch provider, they can often be trusted with high value payloads such as Mars missions, future piloted missions, and government contracts. In this case, the National Reconnaissance Office (NRO) has designed and built another satellite, which will be launched by ULA.
Not to mention that this has been a mission, ready to go for a while. In November of 2019 the Delta IV Heavy rocket for this mission was transported and erected at Space Launch Complex (SLC)-37B. Due to multiple complications with range violations, mechanical and electrical problems found during the Wet Dress Rehearsals - WDR, NROL-44 has been pushed back farther and farther.
Keep in mind that the only purpose of ULA is to boost the satellite into orbit. After it separates from the Delta Cryogenic Second Stage (DCSS), ULA no longer is in charge of the satellites and the NRO takes over. No one knows for sure what the payload is, but it’s speculated that NRO-44 is a combined mission satellite.
NROL-44: Orion 10 (RIO 10, Mission 8306, Mentor 8) - Delta IV-H [D-385] - SLC-37B link
The payload Orion 10/Mentor 8 is an advanced Orion who merged all of the COMINT, SIGINT, ELINT, MASINT, TECHELINT, and OPELINT satellite project programs together into a massive single satellite payload bus which significantly reduced launch rates compared to previous satellites which this 8300 series slowly replaces.
NROL-44 is likely a replacement for the eleven-and-a-half-year-old USA-202, with the displaced satellite taking on a reserve role in the constellation – either providing auxiliary data collection or serving as an on-orbit spare.
This will likely be the start of a new wave of Orion launches, with the NROL-68 and NROL-70 missions slated to fly from the Cape aboard Delta IV Heavy missions in 2022 and 2024 as probable candidates for the next flights.
Regarding the size or mass of the payload the following is known from ULA’s press office.
The 5 meter DCSS orbit insertion vehicle is from Cape Canaveral or Vandenberg capable of lifting several thousand pounds of payload into orbit. The graphic below lists how much to which type of orbit. Unless NROL-44 were prepared to loft itself into a geostationary orbit GEO by being its own third stage, it had a limited size and mass.
Graphic showing ULA rocket Delta IV Heavy’s capacity to loft various payloads to different orbits
From Cape Canaveral 6580 kilos of payload can be put into a geostationary orbit, so NROL-44 is limited by that mass and must put together a satellite with everything needed to perform its duty on station for at least 15 years.
If the United States should decide to launch from French Guiana in South America even more payload can be launched. Polar launches from Vandenberg are usually retrograde sun synchronous orbits, but high inclination 70 degree orbits can be achieved. The price to pay a lesser payload depending on orbit type.
A lot of research goes into minimizing every part in the satellite, improving everything and extending its operative life before it becomes obsolete or is due to be replaced by a new satellite. Propellant requirements are the major drain on satellite performance.
In orbit station keeping is necessary because against all logic the satellite will drift from its place. Gravitational pulling from the Moon, the Sun and Earth's own movements makes it drift through the seasons. A geostationary 24 hour orbit isn’t stable enough without small burns, gyroscopes and modern satellites are therefore employing a high specific impulse system like plasma or ion thrusters.
The Delta IV launch
Five seconds before the scheduled launch, Delta’s three RS-68A engines ignited. At this point, a fireball formed around the base of the rocket. This is caused by the engines igniting residual hydrogen that has boiled off from the rocket.
The process is well understood and harmless but has charred or set fire to the insulation on several previous flights.
Once the three engines had built up to full thrust, Delta IV Heavy lifted off to begin its mission. Liftoff occurred at the T-0 mark in the countdown when the thrust the rocket’s engines are generating exceeds the weight of the vehicle. For the first 9.4 seconds of flight, Delta climbed straight up, before initiating a pitch and yaw maneuver to place it on an easterly trajectory for the climb into orbit.
Shortly after this, the center core throttled down into partial-thrust mode, limiting loads on the vehicle early in the mission and conserving fuel so it can continue to burn after the side boosters separated.
One minute and 18.4 seconds into the mission, Delta reached Mach 1, the speed of sound. A second and a half later it passed through the area of maximum dynamic pressure – Max-Q – where it experienced peak mechanical stress from aerodynamic forces.
Three minutes and 56 minutes after liftoff, the two side boosters engines shut down, with the spent CBCs separating from the vehicle two seconds later. Around this time, the center core throttled back up to full thrust as it continued the boost phase of the mission. Its role in the flight ended with Booster Engine Cutoff, or BECO, at five minutes, 42.8 seconds mission elapsed time.
About six and a half seconds after BECO, the first and second stages separated, with the final CBC falling away from the rocket. The second stage RL10B-2 engine extended its deployable nozzle and initiated its pre-start sequence – with ignition coming 13 seconds after stage separation.
About 42 seconds after the second stage ignited, Delta’s payload fairing separated. The fairing is the nose cone of the rocket which protects the payload during ascent through Earth’s atmosphere and gives the rocket a consistent aerodynamic profile. Once the rocket reaches space, the fairing is no longer needed and can be discarded to reduce mass.
There are two different payload fairings that can be used on the Delta IV Heavy – a composite fairing which was designed for the Delta, and a metallic fairing made of aluminum which was inherited from the Titan IV. The launch will use the latter, which measures 19.8 meters (65 feet) in length.
This is a trisector fairing, meaning that when it falls away from the rocket it separates into three segments, not two as with most contemporary fairings. The metallic fairing was first used on Delta IV for the DSP-23 launch in 2007, and has subsequently been used for all of the NRO’s geostationary launches on the Heavy.
After fairing separation, the mission will enter a media blackout.
Graphic of the three way fairing separation. Note the spacecraft should be Hubble sized
The only likely official updates after this point will be a confirmation of mission success once the NROL-44 payload has separated from Delta IV Heavy. Given that the launch is targeting a geostationary orbit, this will not occur until six or seven hours after liftoff.
In this time, the DCSS upper stage can be expected to perform three burns. The first, which began after separation from the first stage, will continue for about seven minutes. This will establish the upper stage and its payload in their initial parking orbit.
Based on the published flight profile of Delta IV Heavy’s initial demo mission – which was rumored to be simulating deployment of an Orion satellite – after coasting for a little under eight minutes, the rocket will fire its RL10 engine again for another eight-minute burn.
Now in geostationary transfer orbit, DCSS will coast for about five hours before commencing its final burn. This will last for about 3 minutes and 15 seconds, increasing the orbit’s perigee and decreasing its inclination to deploy its cargo directly into a circular geostationary orbit.
Following spacecraft separation, the DCSS will perform a collision avoidance maneuver to take itself out of the geostationary belt and minimize the risks of a future collision with a satellite. DCSS will then have used 1105 second burn time, so how much propellant can be left for a fourth disposal burn? 18 minutes 15 seconds equals 1105 seconds.
The Delta IV Heavy
One of the more powerful rockets currently in operation, the Delta IV Heavy has launched payloads including NROL satellites and the Parker Solar Probe, a mission to study the Sun. All 12 of the previous Delta IV Heavy launches have been successful.
Customers can choose between different payload fairing sizes to better optimize for their specific payload.
Graphic of Delta Heavy IV split in its major parts. Note the generic spacecraft can be Hubble sized
The Delta IV Heavy is a 725,7 ton heavy lift launch vehicle, meaning that it can take bigger and heavier payloads into orbit. It can launch up to 28,000 kg (61,000 lbs) to a 90 degree inclination Low Earth Orbit (LEO) and 14,000 kg (30,000 lbs) to a 27 degree inclination geostationary transfer orbit (GTO).
To accommodate payloads of all sizes, ULA offers two different payload fairing types with three heights both at 5 m (16 ft) in diameter. A 14 meter (47 ft) tall fairing and a 19.1 m (62.7 ft) tall fairing. As types go it's a three part fairing and a two part fairing.
The Delta IV Heavy first stage consists of three nearly identical 40.8 meter - 170 foot boosters strapped together. The Hydrogen and Oxygen tanks hold together 470 000 gallon of liquid propellant in 6 tanks measuring about 1 792 m3 in needed tank volume.
NROL-82 states that 120 000 gallons of liquid Oxygen is loaded. NROL-44 gave me these numbers. Second source found. Is 470 000 gallon of liquid propellant with DCSS +?
Each booster has one RS-68A engine also manufactured by Aerojet Rocketdyne. Together with DCSS and fairing they stand 71,6 meters - 235 feet tall on the launch pad.
The Hydrogen tanks hold 330 000 gallon of liquid Hydrogen chilled to -252,8 0C Celsius or -423 0F Fahrenheit in 3 tanks measuring about 1 254 m3 in estimated tank volume. The three Hydrogen tanks each hold at least 418 m3 cubic meter liquid Hydrogen.
The Oxygen tanks hold 120 000 gallon of liquid Oxygen chilled to below -182,96 0C Celsius or -297,33 0F Fahrenheit in 3 tanks measuring about 454,2 m3 in estimated tank volume. The three Oxygen tanks each hold at least 151,4 m3 cubic meter liquid Oxygen.
The first stage is infamously known for lighting itself on fire just before launch to burn off extra hydrogen. It does this because it needs to get rid of any hydrogen so it does not explode unintentionally during liftoff.
The hydrogen comes from the purging or chilling of the engines prior to ignition. The engine can’t handle the freezing chock of liquid Hydrogen and Oxygen and will split itself apart especially in the turbopump bearings. They will become brittle and shatter.
Each RS-68A engine has the capability to produce 3,160 kN (705,000 lbf) of thrust for a combined 9,420 kN of total thrust. The RS-68A engine has a Specific Impulse of 362 seconds and uses a combination of liquid hydrogen (LH2) and liquid oxygen (LOx).
During the flight, the center booster burned at a slightly slower throttle setting than the two side boosters. This is because the Delta IV Heavy needs all three boosters in order to get enough velocity to pass through the thick parts of the atmosphere. However, after that, they are expended and jettisoned as to not carry any extra weight.
As the vacuum optimized second stage is very efficient, but not very powerful, the Delta IV Heavy burns its center booster longer than other rockets so the second stage will be able to put its payload into orbit.
Continuing up the rocket comes the second stage. The Delta Cryogenic Second Stage (DCSS) is powered by a single, vacuum optimized RL10B-2 engine. For its fuel, the DCSS uses liquid hydrogen (LH2) and for the oxidizer, liquid oxygen (LOX).
The LH2 tank - volume of 38 m3 holding 10 000 gallon LH2 - being on top, it has the job of supporting the payload and the payload fairing and is structurally separated from the other ‘half’ of DCSS. The clearly smaller LOX tank - volume of 23 m3 holding 6 000 gallon LOX - is suspended below it and is responsible for structurally supporting the RL10B-2 engine.
The RL10B-2 was originally built by Aerojet Rocketdyne and first flew in 1998. It has the capability to produce 110 kN (24,700 lbf) of thrust in a vacuum and has a specific impulse of 462 seconds. It will light up at least four times with 18 minutes 15 seconds of burn time and an unknown throttle setting during the mission.
In order to save costs and weight, the gimbal system uses electromagnetic actuators over normal hydraulics; this also increases reliability.
